1. Field of the Invention
The present invention relates to an electronic device and a lid.
2. Description of the Related Art
A technique for mounting electronic components such as semiconductor chips on a substrate and arranging a lid on the substrate to cover the electronic components for sealing is known.
Japanese Patent Laid-Open No. 2007-42719 describes a semiconductor device comprising: a semiconductor package substrate mounted with a semiconductor element; and a lid including a concave portion and a flange portion, the concave portion accommodating the semiconductor element at a center part and including an adhesive side adhered to the semiconductor element, the flange portion located at the periphery of the concave portion and including an adhesive side adhered to the semiconductor package substrate, wherein the semiconductor package substrate and the lid cover the semiconductor element. The relationship between a depth d1 (μm) from the adhesive side of the flange portion to the adhesive side of the concave portion and a length d2 (μm), which is a sum of a height from the adhesive side of the semiconductor package substrate adhered with the flange portion to the adhesive side of the semiconductor element adhered to the concave portion and a thickness of an adhesive filled between the semiconductor element and the concave portion, is 25 μm≦d2−d1≦300 μm. According to the technique, the concave portion of the lid and the semiconductor element can be closely attached to the adhesive when the lid is adhered to the semiconductor package substrate mounted with the semiconductor element, and the semiconductor element and the lid can be surely attached.
Japanese Patent Laid-Open No. 2000-200870 discloses a configuration in which a reinforcing plate is attached by a conductive adhesive resin on a substrate mounted with a semiconductor chip so as to surround the space mounted with the semiconductor chip, a conductive lid member is fixed on the semiconductor chip through a conductive adhesive resin, and the upper side of the reinforcing plate is also adhered to the lid member by the conductive adhesive resin. In the configuration, the reinforcing plate is connected to a ground electrode of a wiring pattern of the substrate for shielding.
However, conventionally, there id a problem that the lid tilts when the lid is attached to the substrate.
FIG. 5 is a cross sectional view of a configuration of an electronic device in which a plurality of electronic components with different heights are mounted on a substrate. An electronic device 10 includes a substrate 2, electronic components 60 and 62 mounted on the substrate 2, and a lid 50. The lid 50 protrudes in the direction opposite the substrate 2 and includes a cover portion 52 covering the electronic components 60 and 62 and a flange portion 54 arranged at the periphery of the cover portion 52 and adhered to the substrate 2.
Solder balls 4 are arranged on the side opposite the side mounted with the electronic components 60 and 62 of the substrate 2. The electronic component 60 is electrically connected to the substrate 2 through solder balls 64. The electronic component 62 is electrically connected to the substrate 2 in flip chip implementation and is adhered to the substrate 2 by an underfill 66.
In the electronic device 10 configured this way, an adhesive 8 is applied to a part facing the flange portion 54 of the lid 50 on the upper side of the substrate 2. A heat dissipation paste 12 is applied to the upper sides of the electronic components 60 and 62. To maintain the strength of the lid 50 and to provide excellent heat dissipation for the electronic components, the heat dissipation paste 12 contacts the electronic components and the lid 50 when the lid 50 is attached to the substrate 2. Therefore, a sufficient thickness of heat dissipation paste 12 is applied to the electronic components. In this condition, the lid 50 is attached to the substrate 2. This leads the lid 50 to adhere to the substrate 2 through the adhesive 8. The heat dissipation paste 12 is arranged between the electronic components 60 and 62 and the lid 50. This can release the heat generated by the electronic components 60 and 62 through the lid 50.
However, since the lid 50 contacts the heat dissipation paste 12 upon the attachment to the substrate 2, there is a problem that the lid 50 is affected by the variation in the upper side height of the heat dissipation paste 12 on the electronic components, and the lid 50 tilts upon the attachment. Especially, the lid 50 tends to tilt against the substrate 2 when a plurality of electronic components with different height are mounted on the substrate 2, or when the electronic components are not arranged at the center of the substrate 2. Conventionally, the tilted lid 50 is adhered to the substrate 2 through the adhesive 8. However, if the lid 50 tilts and the interval between the lid 50 and the substrate 2 becomes wide, the adhesive 8 does not sufficiently spread between the substrate 2 and the lid 50, and an adhesion failure occurs. Furthermore, when the lid 50 tilts, there may be a problem that the adhesion between the heat dissipation paste 12 and the lid 50 is insufficient, causing the heat dissipation characteristics to degrade. Furthermore, when the lid 50 is tilted, there is a problem that the flatness defined in product specifications is not satisfied.